Methyl methacrylate synthesis method, oxidation esterification bifunctional catalyst and preparation method and application of oxidation esterification bifunctional catalyst

Abstract

The invention provides a methyl methacrylate synthesis method, an oxidative esterification bifunctional catalyst and a preparation method and application thereof, the catalyst comprises an active component with a general formula AuRhaOn / MNbOx, N is selected from IIA group elements, and M is a carrier element; a is equal to 0-1 and is not 0; b is equal to 0-1 and is not 0; x and n are numerical values determined by the total valence of elements except oxygen in the general formula; the catalyst has the advantages of high conversion rate and high single yield, the single yield is high when the catalyst is used for synthesizing methyl methacrylate from methyl methacrylate, and the raw material conversion rate is high.

Description

Technical Field

[0001] The invention belongs to the technical field of methyl methacrylate synthesis methods, and specifically relates to a catalyst for methyl methacrylate synthesis, and a preparation method and application thereof. Background Art

[0002] Methyl methacrylate (MMA) is an important organic chemical raw material, mainly used in the production of polymethyl methacrylate (PMMA). PMMA is widely used in industries such as automobiles, construction, sanitary ware and public works. As of 2020, the domestic MMA production capacity has reached 1.455 million tons / year.

[0003] In the current MMA production process, the ACH process route accounts for the largest proportion. It requires the use of an acrylonitrile unit to produce HCN as a by-product. Therefore, it is greatly affected by its operating status and produces a large amount of ammonium sulfate as a by-product. The production cost is relatively high, and the country has restricted this process route.

[0004] Compared with other processes, the direct oxidation method using C4 as raw material has the outstanding advantages of wide raw material sources and green and clean. The MMA production process using C4 as raw material has gradually been promoted in China. The process route is divided into three-step method and two-step method. The three-step method oxidizes isobutylene to methacrolein, which is further oxidized to methacrylic acid, and finally esterified with methanol to obtain methyl methacrylate. The two-step method is to oxidize and esterify methacrolein in one step to produce methacrylic acid. The two-step route has many advantages such as short reaction route, high atomic utilization rate, good selectivity, mild reaction conditions, and greenness. It is an important change in the production of MMA by C4 route, and its catalyst is the key to this technology.

[0005] Currently, most precious metal catalysts are loaded with oxides, especially Au, which has the advantage of high selectivity, but the catalyst cost is extremely high. For example, Suzuki of Japan loaded 1.1wt% Au nanoparticles on composite oxide carriers such as SiO2-Al2O3-MgO, and the catalyst cost was as high as millions per ton. How to improve the catalyst effect and gradually reduce the catalyst cost has become the biggest challenge. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems of low conversion rate and low product yield of the catalyst used in the one-step oxidative esterification reaction for synthesizing esters in the prior art, and to provide a bifunctional oxidative esterification catalyst with high conversion rate and high product yield.

[0007] Studies have shown that Au nanoparticles are very beneficial in improving the selectivity of this reaction, and it is necessary to develop better additives and carriers to promote the activity of gold nanoparticles.

[0008] In order to achieve the above object, the present invention provides a bifunctional oxidative esterification catalyst, which comprises a catalyst having a general formula of AuRh a O n / MN b O x An active component, wherein N is selected from Group IIA elements and M is a carrier element;

[0009] a=0~1, and not 0;

[0010] b = 0 to 1, and not 0;

[0011] x and n are values ​​determined by the total valence of the elements other than oxygen in the general formula.

[0012] The second aspect of the present invention provides a method for preparing a bifunctional oxidative esterification catalyst, the preparation method comprising:

[0013] (1) Preparation of MN b O x carrier, N is selected from Group IIA elements, and M is a carrier element;

[0014] (2) MN b O x The carrier is mixed and contacted with the Au source and the Rh source in a solution state, and optionally dried and then calcined to obtain a catalyst.

[0015] The third aspect of the present invention provides a bifunctional oxidative esterification catalyst prepared by the method of the present invention.

[0016] A fourth aspect of the present invention provides use of the bifunctional oxidative esterification catalyst of the present invention in the synthesis of methyl methacrylate.

[0017] A fifth aspect of the present invention provides a method for synthesizing methyl methacrylate, the method comprising: contacting methanol with methacrolein in the presence of a catalyst to carry out an oxidative esterification reaction, wherein the catalyst comprises the bifunctional oxidative esterification catalyst of the present invention.

[0018] The catalyst of the invention has the advantages of high conversion rate and high unit yield. When used for synthesizing methyl methacrylate from methyl methacrylate, the unit yield of methyl methacrylate is high and the raw material conversion rate is high. DETAILED DESCRIPTION

[0019] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0020] The present invention provides a bifunctional oxidative esterification catalyst, which comprises a catalyst having a general formula of AuRh a O n / MN b O x An active component, wherein N is selected from Group IIA elements and M is a carrier element;

[0021] a=0~1, and not 0;

[0022] b = 0 to 1, and not 0;

[0023] x and n are values ​​determined by the total valence of the elements except oxygen in the general formula. The catalyst of the present invention has the advantages of high conversion rate and high unit yield. When used for synthesizing methyl methacrylate, the unit yield of methyl methacrylate is high and the raw material conversion rate is high.

[0024] According to a preferred embodiment of the present invention, a=0.01-0.5, preferably 0.12-0.19; b=0.01-0.3, preferably 0.1-0.2.

[0025] According to a preferred embodiment of the present invention, the content of the Group IIA element is in the range of 1-50 wt %, preferably 5-20 wt %, calculated as oxide.

[0026] According to a preferred embodiment of the present invention, the Au content ranges from 0.1 to 0.9 wt %, preferably from 0.5 to 0.8 wt %, calculated as oxide. According to a preferred embodiment of the present invention, the Rh content ranges from 0.01 to 0.2 wt %, preferably from 0.04 to 0.06 wt %, calculated as oxide.

[0027] According to a preferred embodiment of the present invention, all Group IIA elements can be used in the present invention. For the present invention, the Group IIA element is selected from at least one of Be, Mg, Ca, Sr, Ba and Rr, preferably Ca and / or Sr.

[0028] According to a preferred embodiment of the present invention, commonly used carriers can be used in the present invention, and the optional range of the carrier element M is relatively wide. For the present invention, M is preferably one or more of Si, Al, Ce and Ti, preferably Si.

[0029] According to a preferred embodiment of the present invention, the size of the Au particles is in the range of 1-10 nm. The use of the above-mentioned preferred catalyst can further improve the oxidative esterification conversion rate and selectivity of the catalyst.

[0030] According to a preferred embodiment of the present invention, the specific surface area of ​​the catalyst is in the range of 100-500 m 2 / g.

[0031] The catalysts having the above-mentioned characteristics of the present invention can be used in the present invention, and there is no special requirement for their preparation methods. According to the present invention, a preparation method of an oxidative esterification bifunctional catalyst is provided, and the preparation method comprises:

[0032] (1) Preparation of MN b O x carrier, N is selected from Group IIA elements, and M is a carrier element;

[0033] (2) MN b O x The carrier is mixed and contacted with the Au source and the Rh source in a solution state, and optionally dried and then calcined to obtain a catalyst.

[0034] In the present invention, MN is prepared b O x There is no special requirement for the method of preparing the carrier. The commonly used methods for preparing the carrier containing active metals can be used in the present invention. For the present invention, it is preferred to prepare MN b O x The carrier methods include impregnation method, co-precipitation method and the like.

[0035] According to a preferred embodiment of the present invention, preferably, MN is prepared b O x The carrier method includes: dissolving the N source in water to obtain solution A, then adding solution A to the M sol, spray drying to obtain a carrier precursor, and then roasting to obtain MN b O x The use of the above preferred technical solution can further improve the oxidative esterification activity and selectivity of the catalyst.

[0036] According to a preferred embodiment of the present invention, the sol of M is silica sol, and further preferably the silica sol is ammonium silica sol, and more preferably the solid content of the silica sol is 5-50% by weight, preferably 35-45% by weight, for example 35% by weight, 40% by weight, 45% by weight. The use of the above preferred technical solution can further improve the oxidative esterification activity and selectivity of the catalyst.

[0037] In the present invention, there are no special requirements for the spray drying conditions, and the commonly used spray drying conditions can be used in the present invention, which will not be described in detail herein. In the embodiment, the spray drying conditions include: inlet temperature 300°C, outlet temperature 150°C, and rotation speed 2w / min as an example to illustrate the advantages of the present invention, but the scope of the present invention is not limited thereby.

[0038] According to a preferred embodiment of the present invention, preferably, MN is prepared b O xThe method for preparing a carrier comprises: dissolving a N source in water to obtain a solution A, impregnating and contacting the solution A with a solid compound of M, and optionally drying and then calcining.

[0039] In the present invention, there is no special requirement for drying conditions, and common drying conditions can be used in the present invention, which will not be described in detail herein. In the embodiments, vacuum drying conditions and drying at 80-100° C. are used as exemplary to illustrate the advantages of the present invention, but the scope of the present invention is not limited thereto.

[0040] According to a preferred embodiment of the present invention, preferably, the N source includes oxygen-containing salts and / or oxygen-containing salt hydrates of one or more elements selected from Be, Mg, Ca, Sr, Ba and Rr.

[0041] In the present invention, there is no special requirement for the method and conditions of roasting. For the present invention, preferably, MN is roasted b O x The conditions of the carrier include: a temperature of 450-700° C., preferably 500-600° C., and 550° C. is used as an example in the embodiment to illustrate the advantages of the present invention, but the scope of the present invention is not limited thereby.

[0042] In the present invention, there is no special requirement for the method and conditions of roasting. For the present invention, preferably, MN is roasted b O x The conditions of the carrier include: a time of 2 to 100 hours, preferably 3 to 6 hours. In the embodiment, 4 hours is used as an example to illustrate the advantages of the present invention, but the scope of the present invention is not limited thereto.

[0043] In the present invention, there are no special requirements for the conditions and steps of calcination in step (2). According to the present invention, the conditions for calcination to obtain the catalyst preferably include: a calcination temperature of 150-550°C.

[0044] In the present invention, there are no special requirements for the conditions and steps of calcination in step (2). For the present invention, the conditions for calcination to obtain the catalyst preferably include: a calcination temperature of 150-550° C., and a calcination time of 2 to 200 hours, preferably 3 to 10 hours. In the embodiment, 4 hours is used as an example to illustrate the advantages of the present invention, but the scope of the present invention is not limited thereby.

[0045] According to a preferred embodiment of the present invention, preferably, the conditions for calcining the catalyst in step (2) include: first calcining in an oxygen-deficient atmosphere, and then second calcining in a pure oxygen atmosphere. The use of the above preferred technical solution can further improve the oxidative esterification activity and selectivity of the catalyst.

[0046] According to a preferred embodiment of the present invention, preferably, the oxygen volume concentration in the oxygen-deficient atmosphere is 2-7%, and the other inert gas is at least one of argon, nitrogen, neon and helium. The use of the above preferred technical solution can further improve the oxidative esterification activity and selectivity of the catalyst.

[0047] According to a preferred embodiment of the present invention, preferably, the temperature of the first calcination is 20-300° C. higher than the temperature of the second calcination, preferably 100-200° C. higher, for example 100° C., 150° C., 200° C. higher. The use of the above preferred technical solution can further improve the oxidative esterification activity and selectivity of the catalyst.

[0048] According to a preferred embodiment of the present invention, more preferably, the temperature of the first calcination is 250-550°C, preferably 300-400°C, and 350°C is used as an example in the embodiment to illustrate the advantages of the present invention, but the scope of the present invention is not limited thereby; the temperature of the second calcination is 150-350°C, preferably 200-250°C, and 250°C is used as an example in the embodiment to illustrate the advantages of the present invention, but the scope of the present invention is not limited thereby. The use of the above preferred technical scheme can further improve the oxidative esterification activity and selectivity of the catalyst.

[0049] According to a preferred embodiment of the present invention, the first calcination time is 1-5 hours. In the embodiment, 2 hours is used as an example to illustrate the advantages of the present invention, but the scope of the present invention is not limited thereby.

[0050] According to a preferred embodiment of the present invention, the second calcination time is 1-5 hours. In the embodiment, 2 hours is used as an example to illustrate the advantages of the present invention, but the scope of the present invention is not limited thereby.

[0051] The invention provides a bifunctional oxidative esterification catalyst prepared by the method described in the invention.

[0052] The present invention provides the use of the bifunctional oxidative esterification catalyst of the present invention in the synthesis of methyl methacrylate. The bifunctional oxidative esterification catalyst of the present invention has high activity and selectivity.

[0053] The invention provides a method for synthesizing methyl methacrylate, which comprises: in the presence of a catalyst, bringing methanol into contact with methacrolein to carry out an oxidative esterification reaction, wherein the catalyst comprises the oxidative esterification bifunctional catalyst of the invention.

[0054] According to a preferred embodiment of the present invention, preferably, the method comprises: performing the process in a tank reactor.

[0055] According to a preferred embodiment of the present invention, the reaction temperature is 60-90°C.

[0056] According to a preferred embodiment of the present invention, the O2 partial pressure is 0.02-3 MPa.

[0057] According to a preferred embodiment of the present invention, the molar ratio of methanol to methacrolein is 10-40.

[0058] According to a preferred embodiment of the present invention, the reaction time is 0.5-24h.

[0059] The present invention is described in detail below in conjunction with the examples. It should be understood that the embodiments and examples described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0060] The catalyst evaluation method used in the following examples is:

[0061] The reactants methacrolein and methanol are added to a kettle reactor filled with the catalyst to be tested, heated to the required temperature, and then a certain amount of air is introduced. Then, the gas chromatography is used for analysis. The carbon balance is calculated during the analysis process, and the data when the carbon balance is 95-105% are selected as valid data. The reaction conditions are:

[0062] Reactor: Tank reactor, volume 200ml;

[0063] Catalyst filling amount: 2 g;

[0064] Reaction temperature: 90°C;

[0065] Reaction time: 3 hours;

[0066] Raw materials: methanol: 58.2 g, methacrolein: 6.4 g

[0067] Air pressure: 3.5Mpa.

[0068] Methacrolein conversion rate = methacrolein consumed in the reaction / methacrolein put into the reaction * 100%;

[0069] Selectivity of methyl methacrylate = number of moles of methyl methacrylate produced in the reaction / number of moles of methyl methacrylate produced theoretically * 100%;

[0070] Methyl methacrylate yield = conversion of methacrolein * selectivity of methyl methacrylate.

[0071] The concentration of each component in the reaction solution was tested using gas chromatography and internal standard method.

[0072] Example 1

[0073] (1) Dissolve 20 g of strontium nitrate (Sr(NO3)2) in water to obtain solution A, then add solution A to 140.4 g of silica sol (SiO2 40 wt%), mix well, and spray dry (conditions include: inlet temperature 300°C, outlet temperature 150°C, rotation speed 2 w / min) to obtain a carrier precursor.

[0074] (2) The obtained carrier precursor was calcined in air at 550°C for 4 hours to obtain the carrier.

[0075] (3) 50 ml of gold chloride solution (Au content 0.005 g / ml) and 5 ml of rhodium chloride aqueous solution (Rh content 0.005 g / ml) were mixed to obtain a mixed salt solution B, which was added to 50 g of the carrier and stirred for a period of time. After the color of solution B turned transparent, it was filtered and washed, and dried in a vacuum oven at 100°C to obtain a catalyst precursor.

[0076] (4) The obtained precursor was first calcined at 350° C. for 2 h in an oxygen-deficient atmosphere with an oxygen content of 2% (V / V) (the rest was nitrogen), and then calcined for a second time in pure oxygen at 250° C. for 2 h to obtain a catalyst for the synthesis of methyl methacrylate.

[0077] Example 2

[0078] (1) Dissolve 22.3 g of calcium nitrate (Ca(NO3)2·4H2O) in water to obtain solution A, then add solution A to 140.4 g of silica sol (SiO2 40 wt%), mix well, and spray dry (conditions include: inlet temperature 300°C, outlet temperature 150°C, rotation speed 2 w / min) to obtain a carrier precursor.

[0079] (2) The obtained carrier precursor was calcined in air at 550°C for 4 hours to obtain the carrier.

[0080] (3) 50 ml of gold chloride solution (Au content 0.005 g / ml) and 5 ml of rhodium chloride aqueous solution (Rh content 0.005 g / ml) were mixed to obtain a mixed salt solution B, which was added to 50 g of the carrier and stirred for a period of time. After the color of solution B turned transparent, it was filtered and washed, and dried in a vacuum oven at 100°C to obtain a catalyst precursor.

[0081] (4) The obtained precursor was first calcined at 350° C. for 2 h in an oxygen-deficient atmosphere with an oxygen content of 2% (V / V) (the rest was nitrogen), and then calcined for a second time in pure oxygen at 250° C. for 2 h to obtain a catalyst for the synthesis of methyl methacrylate.

[0082] Example 3

[0083] (1) Dissolve 22.3 g of calcium nitrate (Ca(NO3)2·4H2O) in water to obtain solution A, then add solution A to an aqueous solution containing 354.1 g of aluminum nitrate (Al(NO3)3·9H2O), continue stirring for a period of time, and spray dry (conditions include: inlet temperature 300°C, outlet temperature 150°C, rotation speed 2w / min) to obtain a carrier precursor.

[0084] (2) The obtained carrier precursor was calcined in air at 550°C for 4 hours to obtain the carrier.

[0085] (3) 50 ml of gold chloride solution (Au content 0.005 g / ml) and 5 ml of rhodium chloride aqueous solution (Rh content 0.005 g / ml) were mixed to obtain a mixed salt solution B, which was added to 50 g of the carrier and stirred for a period of time. After the color of solution B turned transparent, it was filtered and washed, and dried in a vacuum oven at 100°C to obtain a catalyst precursor.

[0086] (4) The obtained precursor was first calcined at 350° C. for 2 h in an oxygen-deficient atmosphere with an oxygen content of 2% (V / V) (the rest was nitrogen), and then calcined for a second time in pure oxygen at 250° C. for 2 h to obtain a catalyst for the synthesis of methyl methacrylate.

[0087] Example 4

[0088] (1) Dissolve 20 g of strontium nitrate (Sr(NO3)2) in water to obtain solution A, then add solution A to 140.4 g of silica sol (SiO2 40 wt%), continue stirring for a period of time, and spray dry (conditions include: inlet temperature 300°C, outlet temperature 150°C, rotation speed 2 w / min) to obtain a carrier precursor.

[0089] (2) The obtained carrier precursor was calcined in air at 550°C for 4 hours to obtain the carrier.

[0090] (3) 80 ml of gold chloride solution (Au content 0.005 g / ml) and 5 ml of rhodium chloride aqueous solution (Rh content 0.005 g / ml) were mixed to obtain a mixed salt solution B, which was added to 50 g of the carrier and stirred for a period of time. After the color of solution B turned transparent, it was filtered and washed, and dried in a vacuum oven at 100°C to obtain a catalyst precursor.

[0091] (4) The obtained precursor was first calcined at 350° C. for 2 h in an oxygen-deficient atmosphere with an oxygen content of 2% (V / V) (the rest was nitrogen), and then calcined for a second time in pure oxygen at 250° C. for 2 h to obtain a catalyst for the synthesis of methyl methacrylate.

[0092] Example 5

[0093] The method of Example 1 is followed, except that the second calcination temperature is 350°C.

[0094] Example 6

[0095] The method of Example 1 is followed, except that the first calcination temperature is 250°C.

[0096] Example 7

[0097] The method of Example 1 is followed, except that the first calcination temperature is 250°C and the second calcination temperature is 350°C.

[0098] Example 8

[0099] The method of Example 1 was followed, except that both calcinations were conducted in an oxygen-deficient atmosphere with an oxygen content of 2% (V / V) (the remainder being nitrogen).

[0100] Comparative Example 1

[0101] (1) 140.4 g of silica sol (SiO2 40 wt%) was spray dried (conditions included: inlet temperature 300° C., outlet temperature 150° C., rotation speed 2 w / min) to obtain a carrier precursor.

[0102] (2) The obtained carrier precursor was calcined in air at 550°C for 4 hours to obtain the carrier.

[0103] (3) 100 ml of gold chloride solution (Au content 0.005 g / ml) was added to 50 g of the carrier and stirred for a period of time. When the color of solution B became transparent, it was filtered and washed, and dried in a vacuum oven at 100° C. to obtain a catalyst precursor.

[0104] (4) The obtained precursor was calcined in air at 350°C for 2 h to obtain a catalyst for methyl methacrylate synthesis.

[0105] Table 1

[0106]

[0107] By adopting the preferred embodiment of the present invention, a high target selectivity can be maintained under a high conversion rate condition.

[0108] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. An oxidative esterification bifunctional catalyst, characterized in that: The catalyst includes a catalyst having the general formula AuRh a O n / MN b O x An active component, wherein N is selected from Group IIA elements and M is a carrier element; a=0~1, and not 0; b = 0 to 1, and not 0; x and n are values ​​determined by the total valence of the elements other than oxygen in the general formula.

2. The catalyst according to claim 1, wherein a = 0.01-0.5, preferably 0.12-0.19; b = 0.01-0.3, preferably 0.1-0.

2.

3. The catalyst according to claim 1 or 2, wherein In terms of oxides, The Group IIA metal content ranges from 1 to 50 wt%, preferably from 5 to 20 wt%; and / or Au content ranges from 0.1-0.9wt%, preferably 0.5-0.8wt%; and / or The Rh content ranges from 0.01 to 0.2 wt%, preferably from 0.04 to 0.06 wt%.

4. The catalyst according to any one of claims 1 to 3, wherein The Group IIA element is at least one selected from Be, Mg, Ca, Sr, Ba and Rr, preferably Ca and / or Sr; and / or M is one or more of Si, Al, Ce and Ti, preferably Si.

5. A method for preparing the bifunctional oxidative esterification catalyst according to any one of claims 1 to 4, characterized in that: The preparation method comprises: (1) Preparation of MN b O x carrier, N is selected from Group IIA elements, and M is a carrier element; (2) MN b O x The carrier is mixed and contacted with the Au source and the Rh source in a solution state, and optionally dried and then calcined to obtain a catalyst.

6. The preparation method according to claim 5, wherein: Preparation of MN b O x The carrier method includes one or more of impregnation method and coprecipitation method; Preferably, the preparation of MN b O x Vector methods include: The N source is dissolved in water to obtain solution A, and then solution A is added to the M sol, spray-dried to obtain a carrier precursor, and then calcined to obtain MN. b O x vector; or, The N source is dissolved in water to obtain a solution A, and the solution A is impregnated and contacted with the solid compound of M, and optionally dried and then calcined; Preferably, the sol of M is silica sol, and further preferably, the silica sol is ammonium silica sol, and more preferably, the solid content of the silica sol is 5-50% by weight, preferably 35-45% by weight; Preferably, the N source comprises oxygen-containing salts and / or oxygen-containing salt hydrates of one or more elements selected from Be, Mg, Ca, Sr, Ba and Rr; Preferably, calcination to obtain MN b O x The conditions of the carrier include: temperature of 450-750° C., preferably 500-600° C.; time of 2 to 100 hours, preferably 3 to 6 hours.

7. The preparation method according to claim 5 or 6, wherein: The conditions for calcining the catalyst in step (2) include: a calcination temperature of 150-550° C. and a calcination time of 2 to 200 hours; Preferably, the conditions for calcining the catalyst in step (2) include: a first calcination in an oxygen-deficient atmosphere, followed by a second calcination in a pure oxygen atmosphere; Preferably, the oxygen volume concentration in the oxygen-deficient atmosphere is 2-7%, and other inert gases are at least one of argon, nitrogen, neon and helium; Preferably, the temperature of the first roasting is 20-300°C higher than the temperature of the second roasting, preferably the temperature of the first roasting is 100-200°C higher than the temperature of the second roasting; More preferably, the temperature of the first calcination is 250-550°C, preferably 300-400°C; the temperature of the second calcination is 150-350°C, preferably 200-250°C; Preferably, the first calcination time is 1-5 h, and the second calcination time is 1-5 h.

8. The bifunctional oxidative esterification catalyst prepared by the method according to any one of claims 5 to 7.

9. Use of the bifunctional oxidative esterification catalyst according to any one of claims 1 to 4 and 8 in the synthesis of methyl methacrylate.

10. A method for synthesizing methyl methacrylate, characterized in that: The method comprises: in the presence of a catalyst, contacting methanol with methacrolein to carry out an oxidative esterification reaction, wherein the catalyst comprises the oxidative esterification bifunctional catalyst according to any one of claims 1 to 4 and 8; Preferably, the method comprises: in a tank reactor, and / or Reaction temperature 60-90°C, and / or O2 partial pressure 0.02-3MPa, and / or The molar ratio of methanol to methacrolein is 10-40, and / or Reaction time 0.5-24h.

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